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[16:30:03] PAMELA BROWN, CNN JUSTICE CORRESPONDENT (voice-over): -- in its second day of searching this lake near the San Bernardino shooting scene hoping to find crucial evidence including the hard drive missing from the couple's computer.

DAVID BOWDICH, ASSISTANT DIRECTOR, FBI LOS ANGELES OFFICE: We did have a lead that indicated that the subjects came into this area and we're seeking evidence of anything that had to do with this particular crime.

BROWN: Investigators are now trying to figure out who the couple might have planned to attack next given the stockpile of explosives and ammunition found at the couple's home following the attack.

SENATOR ANGUS KING (R), MEMBER, SENATE INTELLIGENCE COMMITTEE: What happened in the four hours between the attack and the time these people were killed? They did something during that period. Second gig question is who else were that in touch with? They destroyed their cell phones. We don't have evidence they were in touch with a cell or other terrorists around the country or the world but why did they destroy their cell phones and their computer hard drives?

BROWN: Investigators say Farook became radicalized at least four years ago, but it was only after the San Bernardino attack that the FBI discovered Farook had ties to a radicalized group arrested in 2012 in nearby Riverside, California.

The group planned to kill members of the U.S. military in Afghanistan. Farook's friend, Enrique Marquez, told investigators the arrest of the group is what caused him and Farook to abandon their plans to launch their own attack that same year.

JULIETTE KAYYEM, CNN NATIONAL SECURITY ANALYST: We don't know if this was completely lost and the FBI never saw it or we don't know if they saw some links but didn't have the resources to look at what Farook was doing.

BROWN: Tonight, CNN has learned the FBI is moving away from the idea a workplace dispute that day is what caused the couple to target Farook's office when they did. REPRESENTATIVE ADAM SCHIFF (D), CALIFORNIA: It certainly is very possible that they had other targets in mind, either that day or in the future so what set them off that particular day I don't think we know.

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BROWN: And one reason investigators are moving away from the spur of the moment work dispute theory is because on the day of the attack the couple drove an SUV that they have rented before that day.

No conclusions have been made and investigators remain puzzled about why the office became the target that day. Also adding to this theory that it wasn't spur of the moment was witness interviews as well.

You remember initially the thought was that there was this dispute that happened that day, but now they're looking at something more long-term at the party.

JIM SCIUTTO, CNN GUEST ANCHOR: There are a lot of real questions that remain. It's definitely not cut and dry.

BROWN: And especially what happened in that four-hour gap between when the shooting happened and when they were killed.

SCIUTTO: All right, Pamela Brown, thanks very much for joining us.

SCIUTTO: CNN counterterrorism analyst, Philip Mudd, joining me now. He knows a little bit about it having been counterterror at the CIA. One of the most fascinating things about this is Marquez at this point, right?

He plots with Farook several years ago. They get spooked, don't do the attack and then he's bought these guns already for Farook as well. The idea he suddenly fell out of Jihad and wasn't involved, does that strike you as farfetched?

PHILIP MUDD, CNN COUNTERTERRORISM ANALYST: There are a couple basic questions here. First, in cases like this when someone goes down the path not only of radicalization, we put together radicalization and choosing to commit an act of violence, we have both here, radicalization and plotting in 2012.

We're supposing that reason is taken that leap toward planning a plot that after being spooked by arrests of some locals they said "I'm never in it again. I don't buy it."

The second question I have and the question we haven't determined the answer to is has the FBI picked up his hard drive, his cell phones to say was there contact between 2012 and the 2015 with Farook?

Because to suggest not only that they didn't plot further but that there was no further contact seems farfetched.

SCIUTTO: Can you get those from Marquez without charging him as a person of interest?

MUDD: I would walk in the room and say "you're under suspicion, you were admitting that you were conspiring, a federal violation, in an attack. Give us your information." I'd like to see who was talking to him.

SCIUTTO: How important is the hard drive that they're looking for now? In terms of -- well, answering these questions but also the question about international terrorist groups, et cetera.

MUDD: I think it's critically important because in contrast to cases where you're following the case, you allow it as an FBI investigator to go so far down the path, we don't know who's participating or the target.

Let's say we find the hard drive, one of the critical questions that is unanswered. You go through a radicalization process we know for years. You're married to a spouse who went through that process with you.

You've seen terrorist actors over 15 years starting with the 9/11 attacks who've chosen targets like that twin towers and you end up with a county meeting. I want the hard drive to see, for example, have there been Google searches at targets that might have been what he was looking at.

SCIUTTO: Either primary or possibly secondary after you hit the community center where you had this connection. Philip Mudd, thank you very much. It happens to be your birthday today. Thank you for joining us on your birthday.

[16:35:04]MUDD: It's 21 happy years.

SCIUTTO: Don't look a day over 19. Phil Mudd, thanks very much.

It is like a golden ticket for a terrorist, a fool-proof fake U.S. passport. Now U.S. intelligence is warning that ISIS may be printing them at will, that alarming story after this.

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SCIUTTO: Welcome back to THE LEAD. I'm Jim Sciutto in for Jake Tapper. Topping our World Lead today, a major warning from U.S. intelligence about a new potential threat from ISIS, sources tell CNN that the terrorist group has demonstrated the ability to produce fraudulent passports, which could make tracking terrorist travel between certain countries much more difficult.

Let's get to CNN aviation correspondent, Rene Marsh, tracking late breaking details. They have an actual machine, stolen, I imagine, that makes passports?

RENE MARSH, CNN AVIATION AND GOVERNMENT REGULATION CORRESPONDENT: Right. So a law enforcement official giving me details about what is in the report. It warns that ISIS may have access to a Syrian government passport printing machine and boxes of blank passports. [16:40:10]Now the report also says someone with a fake document may have entered the U.S., but there's no hard evidence of that at this point. What's concerning for Homeland Security officials is these phony passports allow terrorists to hide their overseas travel. Foreign fighters can come and go undetected.

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MARSH (voice-over): The new U.S. intelligence report warns ISIS in Syria may have the capability to create fake passports for travel overseas.

UNIDENTIFIED MALE: Part of the territory they took over happened to have a building where the Syrians processed passports so they have blank passports and the means to print and fake them. This is obvious level of concern we have to pay attention to.

MARSH: U.S. officials are also concerned ISIS may have access to biographical data and fingerprints for Syrian citizens that could be used for phony identifications.

UNIDENTIFIED MALE: The intelligence community is concerned that they have the ability -- the capability to manufacture fraudulent passports which is a concern in any setting.

MARSH: Following the Paris attacks, investigators found fraudulent Syrian passports on two of the terrorists. The U.S. government has since expanded its efforts to flag to other countries suspected documents terrorists could exploit to travel.

Today State Department spokesman, John Kirby, said the department has been aware for some time about the terror group's passport making capabilities.

JOHN KIRBY, STATE DEPARTMENT SPOKESMAN: We have been aware of reports not just in the press that they may have obtained this capability. Obviously it's something that we take seriously.

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MARSH: These individuals cannot travel to the United States using a passport alone. They'd need a visa. In order to get a visa, they need to be screened by the State Department which includes fingerprints. But all that goes without saying that this is a fundamental travel document and wherever fakes are used to circumvent the legal process there's going to be a concern.

SCIUTTO: We talked about how they're a functioning state. They behave like a government and they are printing passports like a government. Rene Marsh, thanks very much.

Coming up next, an exclusive look at a top secret military operation, the Missile and Space Intelligence Center. I'll show you the arsenal of weapons ISIS desperately wants and how they are being used to stay ahead of the terrorists.

And the "New Yorker's" clever cartoons that add a touch of humor to difficult situations. Just how does the magazine select which artists make the cut every week? Inside that decision-making process ahead in our Pop Lead.

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SCIUTTO: Our World Lead now. Could ISIS get their hands on a rocket that could bring down a passenger plane? A secretive military intelligence agency is preparing for that very possibility.

I got exclusive access to America's own rocket program at the military's Missile and Space Intelligence Center and saw their arsenal of dangerous foreign weapons. It's a stash they say might come in handy as they try to stay a step ahead of groups like ISIS.

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SCIUTTO (voice-over): A passenger plane headed from the Netherlands to Malaysia suddenly falls from the sky. Malaysia Airlines Flight MH- 17 brought down near the Ukraine-Russia border by Russian-backed rebels using this surface-to-air missile system known as the BUK.

The ramifications of the strike are far-reaching and incredibly alarming because of who may be trying to obtain similar missiles now.

(on camera): Is there any concern today that terrorist groups would have their hands on something like this?

MARK CLARK, DIRECTOR, DIA MISSILE AND SPACE INTELLIGENCE CENTER: I think it's probably safe to assume at some level there are efforts under way.

SCIUTTO: Folks back home will say my God, look at that missile, can a group like ISIS get their hands on it?

CLARK: It would not be impossible, but we would certainly say that there will need to be some training involved?

SCIUTTO (voice-over): Mark Clark is the director of the Missile and Space Intelligence Center, a branch of the military's own Defense Intelligence Agency or DIA, located far from the battlefields of Iraq and Afghanistan in Huntsville, Alabama, the home of America's own rocket program.

Filling the agency's grounds are a rogue's gallery of dangerous foreign weapons, some captured, some purchased, some acquired by means the DIA won't reveal.

(on camera): So to help train pilots and other war fighters who might come into contact with a weapons system like this in a combat situation they keep these systems operational. This is a fully functioning scud missile.

(voice-over): Proliferation of missile technology preoccupies analysts here more than any other threat.

CLARK: We have greater concerns about the smaller missile threats and the likelihood of the proliferation of those.

SCIUTTO: Small only in size, but not in capability.

(on camera): OK, so this is the SA-7, one of the most common shoulder-fired missiles you'll see out in the world today.

CLARK: Yes. There have been over a million produced, not only this one but other kinds and there's still hundreds of thousands of them out there.

SCIUTTO (voice-over): Today shoulder-fired missiles have targeted some 60 civilian aircraft and you can buy them on the black market for just a few thousand dollars.

(on camera): One of the main dangers of a missile like this is both speed but also ease, that someone like me with no experience can put it together and acquire a target in less than a minute. Sights go up, power goes on, you find your target in the air and you fire your missile. It's incredible.

(voice-over): Often the agency here comes into action after rather than before an attack. This is the first time a reporter has been allowed inside the center's technical analysis room.

[16:50:04](on camera): So it's a CSI for the combat space?

RANDY JONES, CHIEF SCIENTIST, DIA MISSILE AND SPACE INTELLIGENCE CENTER: It's a CSI forensic sort of capability. It's similar to a crime scene investigation. A little bit of DNA here and a fingerprint there begins to piece together a pretty compelling story.

SCIUTTO (voice-over): Within minutes of MH-17's crash, analysts here sprang into action. Desperate to as quickly as possible determine the cause of the crash. As luck would have it, they had visitors that day who could help.

JONES: A group of representatives from across the intelligence community who do just this kind of analysis. We had them here in the building.

SCIUTTO (on camera): So all those experts just happened to be here on that day.

JONES: Just happened timing wise to work out that way.

SCIUTTO (voice-over): As the outside world debated the cause, the DIA had a likely suspect.

JONES: Within an hour and a half we were confident it was a missile that shot it down, a surface-to-air missile that shot it down. We had a fair idea of this one, although we still had home work to do.

SCIUTTO: Homework done at lightning speed. Within hours they were confident they had pinpointed the murder weapon and the perpetrators, telling President Obama that Russian-backed separatists had fired a Russian-made missile that sent nearly 300 people plunging to their deaths.

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SCIUTTO: They had their suspect in 90 minutes and within hours they could say who shot it down where and with what. It was incredible to watch.

Coming up, the world's most controversial, most shocking, most provocative topics simplified in witty cartoons. Now the story behind some of those drawings. That's next in our Pop Lead.

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SCIUTTO: Welcome back to THE LEAD. In our Pop Lead today, the fabled "New Yorker" is very serious business for some cartoonists, or at least very semiserious. Every week, nearly 1,000 cartoons are submitted but only the best, the funniest, the wittiest 15 get picked to be published in the prestigious magazine.

And the man who calls the shots is Bob Mankoff, he's the cartoon editor for the "New Yorker" and he has been a cartoonist for a long time. He's giving us a look into the world of cartooning in a new HBO documentary "Very Semiserious, A Partially Thorough Portrait of "New Yorker" Cartoonists."

I've watched it. Joining me now is Bob Mankoff, the brain behind the "New Yorker" cartoons. Bob, great to have you on today. I have to say, I'll admit that I've been reading these since I was a kid in my parents' magazines and I wonder, there's a great line you have in the documentary.

You say the key to humor is make the strange familiar and familiar strange. I wonder, there's something particular about "New Yorker" cartoons that make them "New Yorker" cartoons. Can you crystalize that? What makes it's a "New Yorker" cartoon?

BOB MANKOFF, CARTOON EDITOR, "THE NEW YORKER": When a new cartoonist comes in and sees me I say "don't try to do cartoons for "The New Yorker," try to do the cartoons you like, hope we like them and hope the readers like them." So there's know focus grouping of it.

It's just cartoonists doing what they want and we're trying to select the best that they do and then we present that to you. So I think it's really unusual in our society where everything is focus group and there's an awful lot of overthinking of things. We like to have the cartoonist do the thinking and be funny at the same time.

SCIUTTO: We saw in Paris with the attacks on "Charlie Hebdo" that cartoons can be in the center of the political conversation even violence in that case. "The New Yorker," you watch it through tragedies like 9/11 and the attacks in Paris and often those cartoons often comment on the time. How do you manage that balance of handling tragedy with humor?

MANKOFF: I think you wait a bit, for one thing. You know, there is something too soon. I'm an absolutist for free speech but not necessarily at all times and at all places so one of the things that cartoons do is, look, I just looked at those two stories that you told about ISIS getting passports and rockets so the world is so fearful.

So one of the things they do, and when it's fearful we become polarized so one of the things the cartoons let us do just by laughing is by making us less fearful and by making us less fearful we can make better decisions.

SCIUTTO: God knows that that's important today. One thing that's changed over time and you've even commented about this. At least the cartoon it's white men. That's changing recently. How do you see that reflected in the art work then?

MANKOFF: Well, for one thing more women are coming in into the magazine. There's enormous push for diversity, as there should be everywhere and that's true in cartooning at "The New Yorker." So we want to definitely reach out to people of color, different ethnicities, that can't necessarily happen overnight, but it's very important for us.

David Remnick has pushed that throughout the magazine that it happens with the cartoons as well as everything else in the magazine and in society.

SCIUTTO: So there's a little bit of a parlor game out there as to whether it's possible that one caption could fit every "New Yorker" cartoon ever and one that's been posited is "hello, I'd like to add you to my professional network on LinkedIn." Do you think there is one?

MANKOFF: And by the way, Jim, I would like to add you to my professional network.

SCIUTTO: I accept.

MANKOFF: You'll be getting an e-mail. Well, that's not a bad one and that's a funny story because when that came out, I printed it on the batch of cartoons I show David Remnick to pick for the magazine. He wasn't aware of that mean, he said "what the heck is this?" I told him about it and we printed one in the magazine.

[17:00:06] SCIUTTO: Bob Mankoff, thanks very much. It's great to have you on. That HBO documentary film, "Very Semiserious: A Partially Thorough Portrait of New Yorker Cartoonists" will debut December 14 on HBO.